Ziegler et al, in U.S. Pat. 4,063,009, describe various polymerization processes suitable for producing forms of polyethylene. Ziegler et al, in U.S. Pat. 4,063,009, describe a catalyst therefor which is the reaction product of an organomagnesium compound (e.g., an alkylmagnesium halide) with a tetravalent titanium compound. The reaction of the organomagnesium compound with the tetravalent titanium compound takes place in the absence of a support material.
Linear low density polyethylene polymers possess properties which distinguish them from other polyethylene polymers, such as ethylene homopolymers. Some properties of linear low density polyethylene polymers are described by Anderson et al, U.S. Pat. No. 4,076,698. Karol et al, U.S. Pat. No. 4,302,566, describe a process for producing certain linear low density polyethylene polymers in a gas phase, fluid bed reactor.
Nowlin et al, U.S. Pat. No. 4,481,301, the entire contents of are incorporated herein by reference, disclose a supported alpha-olefin polymerization catalyst composition prepared by reacting a support containing OH groups with a stoichiometric excess of an organomagnesium composition, with respect to the OH groups content, and then reacting the product with a tetravalent titanium compound. The preferred activator of Nowlin et al is triethylaluminum.
It is a primary object of the present invention to prepare a catalyst composition for the polymerization of alpha-olefins which yields polymerization products having a relatively narrow molecular weight distribution and high bulk density and for production therefrom of films with improved tear strength, FDA extractables, and dart impact resistance.